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Dynamic characteristics of linear rolling bearings for machine tools

Sakai Y., Tsutsumi M.

Journal of Machine Engineering

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2013

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Vol. 13, No. 3

129--142

EN

The present paper proposes a method for evaluating the dynamic characteristics of a single linear rolling bearing subjected to a radial force and a bending moment. In order to evaluate the damping of a rail-carriage system, a rectangular column with a flange is fixed to the carriage by bolts, and the free end of the column is excited by an impulse hammer in the horizontal (x), lateral (y), and radial (z) directions. The response is detected by an accelerometer mounted to the flange of the column. Both force and acceleration are input to an FFT analyzer, and the frequency response function (FRF) is calculated. The damping capacity in each direction is evaluated as a modal damping ratio, which is calculated based on the FRF. As a result, the damping ratio of the vibration mode in the feed (x) direction is higher than those of the other vibration modes. In addition, the influence of the nonlinearity of the linear rolling bearings on the dynamic characteristics is investigated. The results reveal that the dynamic characteristics of the linear rolling bearings depend on the excitation direction.

2

Climatic signal in tree-ring chronologies of Cedrus deodara from Chitral Hindukush range of Pakistan

Khan N., Ahmed M., Shaukat S. S.

Geochronometria

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2013

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Vol. 40, no. 3

195--207

EN

Tree-rings are an important tool for the investigation of paleoclimatic records for regions or periods of time with no instrumental climatic data. However, the responses of different species and sites to various climatic parameters are unusual. In the present study, we developed tree-ring-width chronologies of Cedrus deodara from three different sites of Chitral Hindukush range of Pakistan. The study was conducted to understand tree-growth climate relationship and its applicability in proxy climate investigations. The chronologies covered the past 469 to 595 years, with a mean segment length (MSL) ranging from 148 to 223 years. Climatic data obtained from the three weather stations showed strong correlation and was found useful for tree-ring climate relationships. Correlation Function (CF) and Response Function (RF) analysis showed that spring precipitation (March-May) is a critical limiting factor for tree-ring growth, and temperature prior to November may also play a major role in affecting tree ring-growth. The results exposed that the three sites have con-tinuous relationship indicated that only single species from different locations are affected by the same environmental variables and hence can be used in climate reconstruction in combination. The Cedrus deodara chronologies developed at different locations had several corresponding narrow and wide marker rings indicating a large macroclimatic response to regional climatic conditions. The cur-rent study suggests that the tree-rings of Cedrus deodara from the Chitral Hindukush range could be used to develop chronologies for the reconstruction of seasonal climatic variables.

3

Improvement methods of reconstruction process in digital holography

Paśko S., Jóźwicki R.

Opto-Electronics Review

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2003

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Vol. 11, No. 3

203-209

EN

Problems of quality improvement in holographic images and a reconstruction time reduction are discussed. The convolution and Fresnel approaches are presented. For both methods the algorithm improvement is proposed. Basing on a special transmittance function calculation, a computation time significantly decreases. For the Fresnel approximation, an autocorrelation factor from the reconstructed image is removed. The presented ideas are illustrated by exemplary images for each step of computation. Advantages and disadvantages of the methods are discussed.